Pathology and Genetics

Abstract

PDAC is an aggressive disease and early infiltrates peripancreatic tissues and adjacent organs, and gives distant metastasis and peritoneal involvement, making often surgical resection impossible. About 80% of PDACs are inoperable at the time of diagnosis. However, even if radiologically resectable, some PDAC microscopically involves the resection margins (pancreatic, retroperitoneal, or biliary, the retroperitoneal being the most important because it cannot be evaluated intraoperatorially) resulting in a nonradical excision. Local aggressiveness consists in the invasion of contiguous structures and organs (spleen, stomach, left adrenal gland, colon, and peritoneum), whereas distant metastases can occur in liver, lungs, adrenals, kidneys, bones, brain, and skin.

Most PDACs arise in the head of the pancreas often involving and occluding the intrapancreatic biliary duct and the main pancreatic duct, typically resulting in their upstream dilation associated with jaundice and cholangitis when the former is involved, and cystic formation with a variable degree of scleroatrophy of the surrounding parenchyma when the latter is involved. PDAC can spread through the papilla of Vater and duodenal wall with or without ulceration, raising the problem of differential diagnosis with primary duodenal and ampulla of Vater carcinomas infiltrating the pancreatic parenchyma. Less frequently, PDACs occur in the tail, where they are usually larger at diagnosis, determining weaker symptoms mainly due to loco-regional invasiveness.